Question
Hi!
How deep and how invasive are the root systems of knock out roses? Can they be safely planted near a septic tank?

Thank you for your time!

Answer
Hi Rebecca,
Thanx for your question.  Sorry to take so long.  It has been a busy week around here.  Basically, it is not adviseable to plant trees like willows or poplars near septic tanks.  Many authorities claim that roses are not a problem as they are rather shallow-rooted compared to other shrubs.  I would think that if the roses were set back from the septic system, they will be okay.  I think knockout roses are rather shallow rooted also and I don't think that would be a problem.  Most of the extension services are saying the same thing.  What state and county are you in (if in the U.S.?).  Let me know and I'll see if I can't get you some advice close to your location.
thx,
Tom